In general, conventional blowers can be of a multi-stage or a positive air-displacement type. Conventional blowers enable chemical processing plants and refineries to handle or separate hazardous and corrosive gases, such as vent header off-gassing, spot source, centrifuge venting, or scrubber applications. However, mounting industry pressures to reduce energy and maintenance costs, simplify processes, and improve productivity have led many users of conventional blowers to look for alternatives. Further, because of energy consumption and demanding maintenance requirements, conventional blowers are expensive to operate.
In contrast, regenerative blowers can serve as a practical, efficient, and industry-friendly alternative to help keep costs down and output high. The advantages of regenerative blowers include energy efficiency, low maintenance, and high reliability. As explained below, regenerative blowers also supply clean air and eliminate the need for expensive outlet filters and dryers or special water and oil traps.
In operation, regenerative blowers draw air or other gases into the blower unit by impeller vanes passing an inlet port. The impeller vanes are spaced apart around the periphery of the impeller. Two adjacent impeller vanes capture air and gas from the inlet and centrifugal forces accelerate the air in a radially outward and forward direction. The air is rotated or “regenerated,” by the blower's annular-shaped housing and recapturing of the rotating air between a pair of following vanes, where it is again rotated or “regenerated,” as it enters the space between the following pair of vanes. The successive regenerations imposed on the air and gas impart more pressure to the air and gas.
When the air reaches a “stripper section” at the outlet of the regenerative blower, it is “stripped” from the impeller and diverted out the blower. The stripper section is located between the inlet and the outlet where the annulus is reduced in size to fit closely to the sides and tips of the impeller vanes. As a result, pressures generated by the spinning, non-contacting, oil-free impeller are equal to those obtained by many larger multi-stage or positive displacement blowers.
In summary, regenerative blowers are energy efficient, require little maintenance and are reliable. Regenerative blowers supply clean air and are free of oil, excess moisture, and other compressor-induced contaminants. Regenerative blowers also eliminate any need for expensive, high-maintenance outlet filters and dryers or special water and oil traps. Modern surface treatments of the impeller and internal parts give regenerative blowers the capability to withstand the corrosive, hazardous, and harsh conditions presented by the chemical processing industry.
However, current impeller geometries are relatively inefficient at higher pressure and vacuum duties, as evidenced by sudden drops in air flow and subsequent increases in exhaust temperatures. The typical vane shape of currently available impellers consists of two or three forward bending segments that extend radially outward from the impeller hub. The width of the vane is constant. The central impeller includes a hub having an outer periphery or “volute” that is used to transition the air from axially entering the impeller between two vanes to radially exiting the impeller outer diameter. The volute may be a straight wall that exends radially outward from the hub and that is intersected by the vanes (see, e.g., U.S. Pat. No. 7,033,137, FIG. 2) or the sidewalls may be convex (see, e.g., U.S. Pat. No. 7,033,137, FIG. 4).
There is a need for improved impeller designs, including improved vanes and volute designs that will make regenerative blowers more efficient and therefore more attractive for a broader range of applications.